NEW YORK — Serena Williams’ night started with an ace. And then from there, things went terribly wrong for the world No. 1 and six-time U.S. Open champion.
Williams, needing a win to advance to the U.S. Open final and to keep her No. 1 ranking, played an error-strewn and frustrating semifinal against No. 10 seed Karolina Pliskova, going down 6-2, 7-6(5).
It’s the same stage that Williams lost at a year ago, when the American was looking to complete the calendar Grand Slam — all four majors in one season — for the first time in tennis since 1988.
Such pressure was not lumped on Williams’ shoulders this U.S. Open, but the 34-year-old looked sluggish and slow-footed from the start, broken in the third and seventh games of the first set as Pliskova won it 6-2, in 26 minutes.
The 24-year-old Czech player makes her first Grand Slam final. She had previously never made it past the third round of a major, despite being inside the top 20 for nearly two years.
Pliskova had a break lead early in the second set but lost it when she was broken for the first time in the match in game six. The two traded holds for the next six games, Pliskova serving to stay in the set at 4-5 and 5-6.
She started the tiebreak well, going up 3-0 as groans came from a tense, pro-Serena crowd inside Arthur Ashe Stadium. Pliskova would finish the victory in just under 85 minutes, the biggest win of her career by far.
Williams would rally in the tiebreak behind a series of sensational points, taking leads of 4-3 and 5-4. Pliskova would win both of her points from there, however, and on her first match point, Williams hit a double fault, sending Pliskova into Saturday's final.
"I don't believe it," Pliskova said on court. "Actually, I do believe it ... Serena is a champion. It's never easy to play her. I'm really happy that I stayed there to get the win."
She will play the winner of the later semifinal between Angelique Kerber and Caroline Wozniacki.
"I don't care who is in the final," Pliskova said.
Williams had won her 22nd major at Wimbledon in July, tying Steffi Graf’s Open era record with the victory. But Thursday night’s loss means she will not get to 23 majors this U.S. Open, and her streak of 186 consecutive weeks as No. 1 (dating back to February 2013), is halted.